The development of the petrochemical industry has emphasized the need for means to transfer oil, gas, and other fluids over distances and often under rigorous conditions. The means, to transfer such fluids most often, has taken the form of marine or terrestrial conduits and pipelines. Specifically, in constructing a continuous fluid conduit, the ends of two conduits or pipes are joined axially to form a single conduit that is used to communicate a medium from one point to another, such as between two vessels, containers, other fluid conduits, or combinations thereof.
There are numerous methods currently used in the pipe and pipeline construction industry to obtain a secure joint. These methods employ different types of connectors and can be distinguished by the various ways in which such connectors are employed. The selection of these different methods will usually depend on the overall design requirements of the fluid system. Often, fluid systems comprise identical pipe segments that are welded end-to-end in an abutting relationship. Such welded pipelines, tend to be expensive to construct, and considerable testing must be undertaken to evaluate the integrity of the welded pipe joint. Moreover, this evaluation process must be continuously repeated over the life of the pipeline. In addition to being able to withstand internal pressurization, marine flow lines, for example, must be able to withstand the high external pressures associated with placement along the seabed.
In addition to welded pipelines, a variety of mechanically coupled conduits have been proposed. These mechanically joined conduits are usually constructed of flanges or clamps that result in large diameter joint segments, which cannot be used easily in J-tubes.
Flanged fittings and gaskets are typically used in rigid piping systems, such as water filtration plants, sewage disposal plants, wastewater treatment plants, pumping stations, chemical plants, and refineries. Often times, the flanged fitting is threaded directly onto the pipe. This is accomplished by threading an end of a pipe and threading a compatibly sized flanged fitting. The threaded flanged fitting is then machine-tightened onto the end of the pipe and transported to the field in this joined condition. The threaded flanged pipe is then connected to another flanged pipe, usually by bolting means. In order to obtain a leak-free joint, a gasket may be used between the faces of the two-flanged fittings.
The use of threaded flanged fittings presents several limitations. Specifically, the threaded flanged fitting is custom machined to accommodate the exact diameter of the pipe and to provide a smooth surface across the end of the pipe and the face of the flanged fitting. In addition, extremely high torque is required to tighten properly the flanged fitting onto the threaded pipe. Consequently, one major limitation of this system is that preparation of the flanged fitting and pipe requires sophisticated machinery not usually available on-site where the finished component will be assembled and installed. A further problem with flanged fittings is that the time taken to tighten a large number of flange bolts to the torque, necessary to achieve a good seal between the pipe, gasket and seal, can be considerable. It would therefore be advantageous if the use of flange bolts could be eliminated and the torque needed to achieve an efficient seal reduced without any loss of seal integrity.
Push-on joints and mechanical joints, utilizing conventional threaded connections, have an increased tendency to loosen after a lengthy period of use, especially when repeatedly placed under large bending forces, thereby rendering their use unsuitable for marine applications. Thus, a new fluid connector assembly is needed that can be used with standard pipe or pressure vessels, can be assembled easily in the field, and is equally or more stable and secure than other alternatives now available.
Joining lengths of pipe, tubing, or other fluid conduits by means of a threaded connection typically utilizes the use of a coupling (e.g., a union connector), which generally comprises a short tubular hollow piece that is about one half inch to one inch larger in outer diameter than the pipe and is threaded on its inside diameter. Generally, the coupling is threaded allowing the connection to be uncoupled by unscrewing the pipe, comprising an external thread, from one or both ends of the coupling.
It is desirable in forming a fluid connection that the connector assembly satisfies several functions. Often times, the materials being transported are liquid or gaseous in nature, and particularly in those circumstances, it is desired and needed that the fluid connector assembly provide a seal against leakage between mating threaded elements. This could be achieved by providing, upon makeup of the connector assembly, a seal between faces of male and female threaded elements. Therefore, a need exists for the mating portions of the connector assembly to maintain surface-to-surface contact to prevent leakage therebetween.
Another important design requirement and need exists when it becomes necessary to join the pipe components in a rigid or restrained manner. Specifically, it is desirable that the coupling have the capability to resist tension and thereby prevent the connection from pulling apart when the piping system is subjected to internal pressure or when earth tremors or other external forces contact the pipes. In addition, the coupling preferably should also have resistance to torsion in order to keep the pieces of pipe from rotating relative to the coupling and thereby being disconnected from the coupling. Lastly, a coupling preferably should have structural rigidity to avoid yielding under bending tension or compression stresses, or any combinations thereof.
In order to accomplish these needs, those skilled in the art are constantly in search of improved means for securing ends of fluid conduits to form a sealed fluid connection therebetween. The disadvantages of the prior art are overcome by the present invention.